Cannabis sativa is the most widely used illicit drug in the United States with about 7 million people using it at least once a week. Although the acute effects of cannabis on neuropsychological functions seem reversible, long-term neurocognitive effects and potential psychiatric consequences are not yet fully understood. However, it is important to specify the potential long-term effects of cannabis for several reasons: (1) Cannabis might be used as a treatment for certain conditions in the future, so it is important to determine whether or not cannabis produces long-lasting neurotoxicity; (2) Cannabis use among young people may result in long-term permanent neuropsychological consequnces including cognitive deficits and increased risk of schizophrenia. The present proposal seeks support to examine neurocognitive and psychiatric consequences of cannabis use in young adults. Attention, inhibitory control, and social cognition will be investigated in current and past cannabis users and nonusers at the beginning of the first year of college. They will be monitored regulary during the first year to track changes in behavior in relation to cannabis. In addition, schizotypal personality will be examined in young cannibus users. Cannabis use is implicated in increased risk for schizophrenia and schizotypal personality but it is unclear whether pre-existing liability for psychosis may be a major factor. We will assess schizotypal traits and cannabis use in first year college students and re-examine them a year later to test whether cannabis use increases psychosis-proneness or whether pre-existing schizotypal personality increases the probability of using cannabis. In sum, this project will enable us to further identify and elucidate the potential neurocognitive and psychiatric consquences of cannabis use in young, healthy people and pinpoint possible neural circuits that may be affected by cannabis. The outcome of this project will enable us to design and conduct focused functional and structural neuroimaging studies of adolescent and young adult cannabis users in the future in order to understand how cannabis use may affect neural circuits in late adolescence and early adulthood and whether these potential changes are permanent. Thus the outcome of this proposal will directly form the basis for systematic neuroimaging investigations of the origins of cannabis neurotoxicity and cannabis potential role in psychosis.